Lecture 11- Patterns+ Processes Of Extinction

Question 1

How many earth species are though to have existed in the last 4 3.5 billion years ,and what percentage are now believe to be extinct?

Answer 1

4 billion, 99% extinct

Question 2

How is a mass extinction defined?

Answer 2

As a time period where 3/4 of the diversity of life on Earth is lost in a geologically short interval

Question 3

How are extinction measure? Why?

Answer 3

Number of lost FAMILES as species records are incomplete in the fossil record

Question 4

What has been the direct/indirect driver of the past mass extinction?

Answer 4

Changes in climate

Question 5

What is the background extinction rate?

Answer 5

~1/1000000 per year

Question 6

Which is more vulnerable to extinction, K or R selected species?

Answer 6

K because they are less adapted to changeable environments

Question 7

What are the two reasons for small and isolated populations being vulnerable to extinction?

Answer 7

1. Demographic reasons

2. Genetic reasons

Question 8

How do demographic reasons result in isolated populations being vulnerable?

Answer 8

A lower EFFECTIVE POPULATION SIZE means lower rates of reproduction and lesser capacity to survive extinction pressure. There is also a reduced FECUNDANCY in isolated populations.

Question 9

How do genetic reasons contribute to the vulnerability of small and isolated populations?

Answer 9

The lesser genetic diversity in small populations means a lesser likelihood of effectively coping with environmental change. Moreover, the increased likelihood of defects and offspring mortality from inbreeding makes them less adapt to survival

Question 10

What I’d effective population size and what can it influence?

Answer 10

The number of individuals able to breed in a population

Influence how well equipped the population is towards potential extinction

Question 11

The number of species on earth at any given time can be found via the intersection of what?

Answer 11

The speciation and extinction rate

Question 12

What are the three factors involved in the extinction vortex?

Answer 12

• directional factors
• genetic factors
• stochastic factors

Question 13

Give example of directional factors in the extinction vortex (four)

Answer 13

1. Habitat loss
2. Pollution
3. Over exploitation
4. Exotic species

Question 14

What are the genetic problems in the extinction vortex? (2)

Answer 14

Loss of genetic diversity

Inbreeding leading to poor survival rates

Question 15

What are some example stochastic factors? (Three)

Answer 15

1. Demographic stochasticity
2. Environmental variation
3. Catastrophes